The invention relates to a method for charging the salt space of a latent heat storage means. During charging, the salt space is fully charged with salt heated above its fusing temperature. After charging, the salt space is hermetically sealed.
The storage of latent heat in fusing salt mixtures or even salt solutions is a known practice. It is also a known practice to produce latent heat storage means by charging rigid salt elements with salt in its liquid salt condition, just above the fusing temperature. Further, to avoid the inclusions of air, meticulous topping off is undertaken and the salt space is hermetically sealed. The temperatures occurring during operation are substantially higher than those used for charging.
In order to keep heat losses as low as possible, highly effective thermal insulation is needed for the storage core containing the salt elements. The housing containing the storage core is surrounded by an external housing forming an insulation space. A high vacuum is preferably produced in the insulation space. In order to maintain a permanent vacuum as long as possible, the surfaces facing the insulation space of the inner and of the outer housing and possibly the internal structures, have to be degassed In the insulation space. A baking operation whose temperature is also substantially greater than the fusing temperature is used to enhance the degassing of the insulation space.
The fusion or transition temperature in the case of conventional latent heat storage means is about 70.degree. C. The salt elements are charged at a slightly higher temperature. The maximum operating temperature is at 125.degree., while a desired baking temperature is about 400.degree..
Both the temperature occurring during operation and occurring during baking may lead to a substantial pressure build-up in the salt space, especially if the boiling point of the salt-mixture is exceeded.
In order to tackle the problems in this connection the practice has been adopted of dividing up the salt volume into separate elements. The separate elements are in the form of flat, thin walled bodies in order to make possible changes in volume, which are caused in operation or in production. However this leads to the further disadvantage that it is awkward to charge a large number of separate elements. Also, economic topping off is not possible and in the case of assembly, at relatively low temperatures, one has to allow an expansion space between the individual salt elements and their supports.